What is Uranium?

Uranium was discovered in 1789 by German chemist Martin Klaproth in an ore known as pitchblende.
It was named after the planet Uranus discovered eight years earlier. Uranium was formed in our solar system by supernova events billions of years ago. Today, its
slow radioactive decay provides the main source of heat inside the earth's crust. Uranium is a heavy metal that can be used as an abundant source of concentrated energy. It usually occurs as an
oxide; one primary uranium mineral is uraninite (UO2). Uranium metal is about 60 percent denser
than lead and almost as dense as gold. It occurs in trace amounts nearly everywhere on the planet, even in seawater.

Clean Energy Source

Nuclear energy produced from uranium is recognized as a practical, inexpensive, and clean
source of energy. A typical 1,000-megawatt reactor can provide enough electricity for a modern
city of up to one million people. Nuclear power very is reliable, and power plants emit no carbon dioxide.
The emissions coming from the massive towers of a nuclear plant are actually water vapor.
Nuclear power boasts the best capacity factor of all forms of electrical generation.
The capacity factor of a power plant is the ration of its actual output for a period of
time to its potential output if it were possible to operate at full capacity as designed
and engineered for that same period of time.
A nuclear power plant can run at above 90 percent capacity; a coal-fired plant runs at about 64 percent,
a natural gas power plant at 43 percent, and a hydroelectric plant at about 40 percent.

In a nuclear-fueled power plant, water is turned into steam, which drives turbine generators to
produce electricity. The main difference between a nuclear power plant and a coal- or natural
gas-fired power plant is the source of heat. At a nuclear power plant, the heat to make the steam
is created when uranium atoms split by a process called fission. There is no combustion in a
nuclear reactor, as opposed to those powered by fossil fuels.

Properties of Uranium

Uranium occurs naturally as three primary isotopes (elements with the same number of protons
but different numbers of neutrons). More than 99 percent of all uranium is 238U (atomic weight
238, or about 238 times the weight of one hydrogen atom and 13 times denser than the same volume
of water), and less than 1 percent is in the form 234U.
The 235U isotope is less stable and thus decays more rapidly than 238U, and is the isotope used
as fuel in nuclear reactors.

Naturally occurring uranium is found as 238U (99.284 percent of all uranium found in nature),
235U (0.711 percent), and a very small amount of 234U (0.0058 percent). Other isotopes of uranium
are known but are very rare and usually short lived. Uranium decays slowly by emitting alpha
particles. An alpha particle emitted from the uranium nucleus is positively charged and made up of
two protons and two neutrons, which is physically and chemically identical to a helium nucleus.
The 238U isotope is useful in dating the ages of some rocks and geologic events.

Uranium Atom

The nucleus of the 235U atom comprises 92 protons and 143 neutrons (92 + 143 = 235). When the
nucleus of a 235U atom captures a moving neutron, it splits in two atoms (fission reaction) and releases energy in the form
of heat and radiation, and two or three additional neutrons are expelled from the nucleus.
If enough of these expelled neutrons cause the nuclei of nearby 235U atoms to split,
releasing additional energy and neutrons, a fission "chain reaction" can be achieved. When this
happens repeatedly, many millions of times, a very
large amount of heat is produced from a
relatively small amount of uranium.